# The specific heat of steel is 420 J/(kg°C). How much energy is required to heat 1 kg of steel by 20 °C?

##### 1 Answer

#### Explanation:

The **specific heat** of a substance tells you how much heat is required in order to heat *one unit of mass*, usually

In this case, the specific heat of steel uses

Since you have

#c = "420 J kg"^(-1)""^@"C"^(-1)#

you can say that you need

This means that in order to increase the temperature of a given mass of steel by

#20 color(red)(cancel(color(black)(""^@"C"))) * "420 J"/("1 kg" color(red)(cancel(color(black)(""^@"C")))) = "8400 J kg"^(-1)#

For

#1 color(red)(cancel(color(black)("kg"))) * "8400 J"/(1color(red)(cancel(color(black)("kg")))) = color(darkgreen)(ul(color(black)("8400 J")))#

I'll leave the answer rounded to two **sig figs**.